Switch



P. S. BEAR Oc'f. 11, 1938.

.swITcH 2 Sheets-Sheet 1 Filed April ll, 1936 1,114 willi,

Oct. l1, 1938.

P. s'. BEAR SWITCH Filed April 11, 1936 2 Sheets-Sheet 2 lil fai-:lss-ur-:n

Patented Oct.1`11938 JUN 3- 1941 PATENT- olrlcr.A

SWITCH Paul S. Bear, Elkhart, Ind., assignor, by mesnc assignments, to Bucklen-Bear Laboratories, Inc., Elkhart, Ind., a corporation of Indiana Application April 11,

1936, Serial No. 73,883

24 claims.' (cl. zon-152) This inventionrelates to switches, and more particularly is directed to switches of the metal envelope type employing mercury as the contactor between spaced metallic electrodes.

In my prior copendlng application, Serial No. 745,842, September 28, 1934, I have disclosed a switch construction employing a cup-shaped metal shell of stainless steel or the like, having an enlarged open end receiving a refractory or ceramic member sealed in the end of the shell and supporting a second electrode in spaced relation to the shell. The present invention constitutes a modification in the design and assembly of such type of mercury switches for imparting 1.; to such swtchesimproved operating characteristics.

I have .found that a mercury switch can be provided having greatly improved operating characteristics by treatment of the mercury itself, as described in the copending application of lmyself and Herbert E. Bucklen, Serial No. 67,816, filed March 9, 1936. With this improved mercury contacting body, and the employment of a liquid alkaline 1111,' such as trlethanolamine, a switch can be produced which is capable of carrying relatively high current, and which can give consistent repeat performance by reason of the retention of astable body of mercury in contact with the second electrode. 30 Reference is made 'to my copending application ,Serial No. 53,146, led'December 6, 1935, for a full disclosure of these features.

The present invention, in its preferred form, is directed to the provision of a metal envelope type of switch having an internal construction such that a greatly increased area of contact between the two contacting bodies of mercury, or between a moving body of mercury and a stationary electrede, is produced, whereby the capacity of the switch is increased to an. extent not hitherto possible in switches of this type. This is accomplished by providing a polygonal-shaped envelope with a ceramic,insert having a planar runway across which the moving body of -mercu-ry moves into and out of contact with a retained stable body of mercury which is in contact with the electrode. The stable body of mercury `lies in a straight line along a sharp cutting edge and presentsy an area. of contact which is considerably increasedover that provided with the usual cylindrical type of metal switch. In effect, I obtain a straight line advancing edge cf mercury and vretain a straight line contacting surface of mercury whereby a greater crosssection of mercury comes into simultaneous 99D- tact, as distinguished from the 'substantially point contact that occurs when two curved surfaces are brought into contact.

Also, heretofore, when the switch' was slowly tilted toward circuit closing position, consider- 5 f able frying and sputtering of the contact surfaces occurred as they moved into engagement. With the present construction, a slow motion closing of the circuit is possible without these attendant disadvantages, and the capacity of the switch is considerably increased without any danger of such frying or sputter-lng. Even on lamp loads, where the closing arc is excessive, tending to produce overheating of the interior of the switch, the present design of switch takes care of such operates under such loads at temperatures only slightly above the adjacent room temperature.

The mounting of the ceramic insert Ain the switch envelope as disclosed in the present construction is such that no portion of the ceramic is placed under tension, the sealing gasket and the support of the ceramic in the metal envelope being such that the ceramic is subject only to compression stresses. This materially lessens any danger of cracking of the ceramic during operation of the switch when internal pressures may be developed due to heating or the like.

Another feature of the present invention is the positioning of the ceramic in thermal contact with the metal envelope, whereby any heating of the ceramic will be dissipated by radiation from the-external surface of the envelope. This materially increases the capacity of the switch to high currents, since the heat generated upon making and breaking of contact ,in a high capacity switch is thus readily dissipated externally c of the switch.. In this connection, I employ a refractory material that is thermally conductive, so that no localized heating of any portion of the ceramic is possible. The use of a limited alkaline' liquid ll is also instrumental in affording dissipation of heat to all portions of the switch envelope.

The ceramic employed in the present switch is designed in such manner as to provide a. relatively long leakage path between the central electrode supported in the ceramic and the surrounding wall of the metal envelope, thereby eliminating any tendency of shorting the circuit` between the electrode and the envelope across the ceramic externally of the switch chamber. By the use of the present construction, producing the elongated leakage path, I also provide for the resilient gasket which seals the ceramic u loads easily without any material heating, and c Vius in position in the envelope to engage the ceramic in such manner as to subject the same to com-l pression, so that' any internal pressures developed in the throat of the ceramic serve onli7 in overcoming this compression stress, and do not place'any tension upon any portion of the ceramic.

The present construction is also advantageous in that the diameters of the electrode supported in the ceramic and of the retaining ring which is employed to compress the gasket during the assembly of theswitch prevent any shear stresses being placed upon the ber members enclosing the outer face of the ceramic. This prevents, to a large extent, any danger of the internal pressure being such as to force the electrode axially outwardly of the switch envelope, since the intermediate gasket means between the outer face of the electrode and the compression ring will be subjected to stresses other than straight shearing stress, and consequently have a much greater resistance to such movement of the electrode. K

My invention also contemplates the provision of a switch assembly havingA a novel type of contact lug retaining washer, the entire assembly being capable of being enclosed within a mol-ded case formed of a phenol condensation product or the like, and capable oi' adjustment so that relation, as desired.

A Astill further advantagesecured by the present invention is the provision of a construction such that maximum contact area is provided between the retained body of merc and the surface ofthe electrode, whereby he resistance to current passage between thelmercury and the electrode is reduced, so that a suicient area of contact is provided to prevent any overheating at this portion A,of the switch.

I also contemplate, in the present switch construction, the enclosing of the switch within a water jacket or the like, whereby the switch may operate under heavy loads and any heating which' may occur will be readily carried away by the circulating water in direct contact with the external surface of the metallic envelope.

I also provide a Vmetal envelope having two diameters, whereby the enlarged portion of the invention will appear more fully from the following detailed description, which, 'taken in conjunction with the accompanying drawings, will disclose to those skilled in the art the preferred construction and operation of the present inventiomn In the drawings: Figure 1 is a vertical sectional view through aswitch embodying the principles of the present invention; c

Figure '2 is a vertical sectional vi'ew through a modified forml of switch;`

Figure 3 is a sectionalview taken substantially on line 3-3 of Figure 2;

Figure 4 shows the mounting of a switch embodying the principles of the present invention within a moi-ded case;

Figure is ,a sectional view taken substantiallv on line 5-5 of Figure 4;

Figure 6 is an elevational View of the contact lug retaining washer shown in Figure 4;

` tion I3 of the enveiope, is inserted into position,

its position being determined with respect to the portion I of the envelope by means of the aligning groove I formed in the ceramic insert and engaging over the struck up boss .I6 in the envelope.

. The portion I0 of the enveloperis preferably `square in section, although it may be of any desiredpolygonal shape, and contains the moving body of mercury I1, vwhich mercury may be cleaned and treated in the manner disclosed in my above mentioned copending application. The ceramic I4 is provided with an inclined frusto-pyramidical opening I8, terminating at the smaller end in a sharp cutting edge i9 devfined by the walls 20 which extend normal to the axis of the ceramic. A suitable electrode 22, which is in the shape of a circular disc member and which is provided with the extending stud portion 23, isspaced outwardly of'the 'I'he ceramic I4 is provided with an axially extending annular ange 24 within which the electrode 22 is seated, and a suitable cup-shaped resilient gasket 25, which may be formed of synthetic rubber or the like, is disposed about the extending portion 23 of the electrode and has the annular flange portion 26 disposed about the flange 24 of the ceramic `and in engagement with the internal surface of the portion I2 of the envelope. The gasket is compressed against the internal surface of the portion I2 of the envelope and against the externalsurface of the ange 24 by means of the fiber washer 21 which is carried about the stud 23 and which engages the rear face of the gasketJ 25. v'Ifne' washer 21 is urged inwardly by means of the compression ring 28, formed of any suitable material, which is L moved inwardly by beading over the end 29 of the portion I2 of the envelope. This beading or spinningover of the end 29 compresses the gasket` 25 in position to seal the space between the walls 20 and closes the outer end of the opening external surface of the ceramic and the internal surface of the portion I2 of the envelope, and to also seal any clearances which may be provided between the internal surface of the ange 24 and The stud portion 23 of the electrode 22 is pro- 75 vided with a suitable nut 30 threaded thereon, which engages a washer 32 that serves to compress the washer 21 against the gasket 25. If desired, arsuitable insulating spacing bushing 3l may be provided to position the washer and nut out of a possible ilash-over position with respect to the vcompression ring and edge of the envelope.

I preferablyy form the ceramic Il of porcelain, inV that porcelain is a thermal conductor having a conductivityv rating which, while not as good as iron, isin close proximity thereto. Furthermore, porcelain is free from metallic oxides that give ofi free oxygen in areasV subjected Vto anr electric arc, and therefore the use of a porcelain ceramic insures that no impurities will'bevintroduced into the interior of the switch envelope which might prove deleterious to switch operation. Certain ceramics, such as those known commercially as Alsimag" andv Isolantite, while perfectly adapted for use as far as mechanical fitting of parts is concerned, are not desirable in alswitch of this construction, since they are relativelyv poor thermal-conductors, that is, excellent thermal insulators. This means that when an arc is impinged upon a given point repeatedly in a ceramic of this latter typethe heat builds up at that point and is not conducted away to any other portion of the ceramic. As

` this heat approaches a given point, the metallic oxides in. this type of ceramic are reduced, and the oxygen attacks the mercury and the unreduced particles that spall oil' are floated on topof the mercury, or form an emulsion with thel triethanolamine. Continued usagel of ceramics of this type erodes a channel through the dam forming the retaining recess until the -retaining recess no longer is capable of retaining any mercury. On the other hand, porcelain, being a good thermal conductor, no localized points of heating will build up, since the porcelain will rapidly conduct the heat away from the localized point oi heat generation to all portions of the ceramic, and this ceramic being in thermal contact with the metal envelope surrounding the same, the heat will be readily dissipated to ad- 'between the ceramic and the surrounding iron envelope, consequently balancing the pressures upon opposite sides of the ceramic so that nc tension stresses are produced which might tend to crack the porcelain.

I iind that ample sealing is secured by employing a gasket having only a relatively short skirt or ilange 26, which seals the outerface of the porcelain and4 yet does not confine any heating of the porcelain so that dissipation is eliminated. It is desirable that any heat generated due to arcing within the switch be dissipated as rapidly as possible through the porcelain to the enclosing metallic envelope.

By the use of a polygonal shaped envelope in which the body of mercury I1 is capable of moving, I provide .for a substantially straight line advancing edge of the mercury as it moves upwar'dly over the inclined planar surface Il. l Similarly, the use of a square opening in the ceramic permits the retained body of mercury vshown in. Figure l retains a body 4of mercury which is of a width such as to have inherent stability. The advantages of the retention onsuch a stable body of mercury whose meniscus lrises above the sharp cutting edge over which contact is made and broken have lbeen pointed out in detail in my copending application, Serial No. 53,146, filed December 6, 1935.

I have -found that by changing from a cylindrical form of switch to the polygonal envelope type of switch, an increase. in effective contact area, when lthe envelope type is of a diagonal dimension substantially equal to the diameter of the cylindrical type, is employed, is increased approximately 300% over the area provided in a cylindrical type of switch of the same external dimension. 'I'his means that a material reduction inthe heating caused by the arcing produced at the contact is effected, and also, currents of much greater capacity can behandled by a switch of this present construction.

.Referring now in detail to the construction shown in Figure 2, this ilgure discloses a modified form ofswitch in which the metal envelope I0 is provided with a normally extending shoulder I2 and the cylindrical portion I3', the square shoulder llpserving as an abutment for limiting the inward movement of the .ceramic I4'. The remaining details of the construction arev substantially as described in connection with Figure 1, the ceramic I4' being provided with a square type of'opening Il having planar inclined runway surfaces, the ceramic Il being aligned with respect to the square portion III' of the envelope by means of the aligning pin engaging in a suit-4 able recess formed in the ceramic Il. Similar reference numerals have been employed to indicate similar parts of the construction.

Aswill be apparent from the structure shown in Figure 3, the body of mercury I1 moves up lthe planar inclined surface I8 into contact with the retained body of mercury 33 retained in the rectangular groove formed between'the face of the electrode 22 and the wall 20 deilnng the sharp cutting edge I9 at the inner end of the inclined surface I8. 'I'he entire width of the surface I8 is therefore occupied by the advancing edge of the body of mercury I1, and the entire width of the cutting edge I9 is also contacted by the retained body o'f mercury 33.' Consequently, as the moving same 'time providesv suiilcient mercury so that a by the occur due to the relatively small contact area be- S tween the retained body of mercury 33 and the surface of the electrode 22 with which the mercury is in contact. In order to prevent any such overheating and to insure that sufficient metal to mercury contact is provided for all currents lwhich may be handled by the switch, I have provideda construction such as shown in Figure '1 `in which the ceramic 48 is provided with the rearwardly extending annular flange 42 defining with the inclined planar surface 43 a square shaped grooveextending about an annular groove v44. Within thisannular groove 44 I dispose a cupshaped electrode 45 'having the cylindrical flange portionv46 lying in and determining the outer periphery of the' groove. Disposed within the groove 44, and retained between the inner face of the electrode 45 and the inner defining wall of the groove is a body of mercury 41 which has a substantially increased contact area in engagement with the surface of the electrode 45. Consequently, the mercury to electrode contact area is increased to anextent such that no overheating can occur because of the passage of higher current of the body of mercury 41 to the electrode 45. Ihe electrode 45 is provided with a stud 48 extending rearwardly therefrom, and the usual resilient gasket 25 having the extending flange portion 26 is provided forvsealing the ceramic in position.

It is believed obviousthat the form of the electrode 45 may be -varied to a considerable degree without departing from the underlying prin- I. ciple'of providing an increased contact area between the retained body of mercury and the engaged face of the electrode. An electrode of the type such as shown at 22 may, for example, be provided with a polygonal recess 2| cut into the face thereof at a point disposed adjacent'the retained body of mercury 33, so thata portion of this mercury is capable of entering the groove to increase the contact area of mercury with the metal of the electrode.

Considering now in detail the structure shown in Figures 4, and 6, I provide a metal envelope having the square section 58, having the normally extending annular shoulder portion 52 and the enlarged cylindrical portion 53 within which is disposed a ceramic insert 54 having a square opening therein indicated at 55 which extends substantially flush with lthe level of the oor surface of the envelope 50 upon which the body of mercury 56 is disposed. The ceramic 54 is provided with an annular ange portion 51 which receives the electrode 58, this electrode having a square head portion of reduced size indicated atV 59 and shown in detail in Figure 5.

A resilient gasket 68 having the short skirt portion 62 engaging about the annular ange 51 is pressed into position by the compression washer 63 which is urged inwardly against the rear face of the gasket68. This seals the ceramic 54 with lrespect to the internal surface of the shell 53,

'- and also seals the electrode 58 with respect to the flange 51 to provide a relatively long leakage path between the electrode 58 and the interior surface of the shell portion 53.

The reduced portion 59 of the electrode 58 is provided with curved surfaces 64 which are in the "form of meniscus curves, land provides for full surface contact ofthe advancing straight edge of the body of mercury 56 along the horizontal portion of the curved surface 64 in order to insure that the greatest cross sectional area of mercury will come into contact with the electrode upon closing of the circuit.

A suitable contact lug retaining washer indicated at 65 in Figure 6V is provided for disposition against the outer face of the compression washer 63, and is held in position by the compression ring 66 formed of metal or the like, which is held in position by the spun-over end 61 of the portion 53 of the metal envelope. The contact lug retaining washer 65 is provided with a struck out tongue portion 68, which has a pair of curved formable nger portions 69 adapted to receive and engage the end of a conductor lead 10. A spacing bushing 12 is disposed within the opening 13 formed in the member 65, and 'serves to space a second insulating washer -member 14 from the spun-over end of the envelope, in order to insulate the lead 18 from the other conductor lead which is connected to a suitable lug 16 carried by the stud portion 11 of the electrode 58, the lug 16 being held in position by the clamping nut 18.

In the embodiment of the invention disclosed, the leads 10 and 15 come out from opposite sides of the switch, but it is obvious that, due to the provision of the insulating washer 14, the leads 10 and 15 can both come out at the same point in the periphery of the switch, if desired.

The metallic switch envelope is venclosed in a suitable moldedphenol condensation product casing 88 which is molded to form and ts rather snugly over the portion 50 of the envelope, and the portion 53 thereof, extending to a point disposed approximately in the` plane of the insulating washer 14. An end cap or mating closure member 82 is provided which extends over the end of the stud 11 and encloses the contact lug 16 having a tongue and groove engagement indicated at 83 with respect to the portion 80 of the enclosing casing, whereby the two casings may be cemented together. Each of the casings is provided with corresponding openings 84 and 85, which serve as lead outs for the conductors lli and 15, respectively. It is obvious that if the two conductor leads are toA be led out from the same portion of the casing, the closure member 82 will be rotated 180 degrees from the position shown in Figure 4, whereupon the opening 85 will be aligned with the opening 84 and the conductors 10 and 15 will be led out from the same side of the casing, being spaced by the insulating washer member 14.

The operation of the switch shown in Figure 4 is similar to that shown in the other figures, except that a mercury to metal contact is provided instead of the mercury to mercury contact provided in the previous switch embodiment. It is, of course, obvious that the vinsulating enclosing cover formed by the members 80 and 82 can be equally well applied to the switches shown in Figures 1 and 2, and will function in the same manner with respect to these switches as described in connection with Figure 4. In such cases, the contact lug retaining washer and the insulating bushing 12 will be applied vto the stud in order to provide for connection of the cor.- ductors thereto. f y

Considering now in detail Figure 8, I have disclosed in this ilgure a switch member 98, provided with the insulating molded cover comprising the two sections 92 and 93 corresponding to the members an and a2 of Figure 4, n1 this embodiment of the invention,'however, the two confits over the enlarged surface of the metallic envelope of the switch, the casing 92 being cut away for this purpose, and provides an annular space 98 about the reduced portion of the switch envelope, which portion 98 is adapted to containV and breaking currents of considerably greater capacity than in any previously designed switch of this type and which is capable of operating with a minimum of heating, since the contact area is increased to an extent such that a considerably greater cross sectional area of mercury comes. into simultaneous contact upon making of the circuit, as compared to the point-to-point contact ordinarily produced by rounded or curved surfaces.

Also, by the use of a ceramic refractory which is heat conductive, and which has good thermal contact with the metal envelope, I prevent any localized overheating of any portion of the switch, since the 'ceramic will conduct away the heat of localized arcs to the vswitch envelope. Other features of my invention, such as the relatively l long leakage path between the 'electrode and the metal shell, and the disposition of the ceramic in the shell in such manner that the sealing means applies only compressive stresses thereto, and no internal stresses upon the ceramic are set up, are believed to provide a switch having greatly improved operating characteristics.

While I am aware that various changes may be made both in the arrangement of parts and design of the structure disclosed, I do not intend to limit myself to the specific details shown and described, and my invention is to be understood as limited only by the spirit and scope of the appended claims.

I claim:

1. A mercury switch of the class describe from said other electrode to said recess, said last' named body of mercury being movable along said oor toward said rst electrode upon tilting of said switch with a straight line advancing edge extending parallel to said face portion and moving intosimultaneous full length contact with said transversely extendingbody of mercury.

2. A mercury switch of the class described have ing a cup-shaped metal envelope, a ceramic insert and an electrode extending normal to the axis of said envelope and supported solely by said insert, a body of mercury in contact with said envelope, a body of mercury extending parallel to one face of said electrode in contact therewith, and a planar runway formed in said insert between said bodies of mercury and a recess at one end of said runway retaining said second body of mercury against movement and in transverse position across the'full width of said runwayv whereby said bodies of mercury make and break contact between parallel faces extending substantially the full width of said runway.

3. A mercury switch comprising a square metal envelope having an enlarged cylindrical end portionvjoined thereto by a frusta-conical section, a ceramic insert in said enlarged portion having a frusto-pyramidal recess extending axially thereof, a disc-shaped electrode closing the small end of said recess and spaced therefrom to define therewith a peripheral rectangular groove, a body of vmercury retained in the lower side of said groove and having the meniscus thereof projecting above the edge of said recess for the full width of the small end of said recess, and a secsupported within said flange, resilient sealing means engaging the outer radial face of said flange and electrode and having a peripheral flange portion disposed between said flange and the inner surface of said enlarged end of said envelope,'a frusto-pyramidal recess in said refractory having its small end spaced from said electrode by an inwardly opening groove, a body of mercury retained in said groove and presenting a contact surface extending parallel to the face of said electrode, and a body of mercury in said envelope movable along one surface of said recess andhaving an advancing edge parallel to the contact surface of said first body of mercury.

5. A switch comprising a metal envelope having an enlarged lopen end portion, a ceramic in contact with the internal surface of said end portion and having an axially extending flange at the outer end thereof spaced inwardly of said surface, av disc-shaped electrode seated within said flange, and resilient sealing means engaging the outer radial surface of said electrode and said flange and having a peripheral axially extending flange disposed between the ceramic ange and the internal surface of said end portion.

6. A switch comprising a metallic envelope, a thermally conductive ceramic in one end of said envelope having thermal contact about its annular peripheralsurface with the internal surface of said envelope, an electrode supported solely by said ceramic and insulated thereby from said envelope, a body of mercury retained in contact with said electrode, a frusto-pyramidal recess lin said-ceramic extending outwardly from said retained body of mercury to the interior of said envelope, and a body of mercury in said envelope movable along a dening surface of said recess into and out of contact with said retained body of mercury.

7. A switch comprising Va metallic envelope having an enlarged cylindrical end portion, a ceramic insert'therein having an axially extending annular ange spaced radially inwardly of the interior of said enlarged portion of said envelope, an electrode disc seated within said flange whereby the leakage distance from said disc to said envelope includes at least' two surfaces of said ange and the radial distance from said flange to the interior of said enlarged end of said `the outer face of' said electrode `anddlange and having a peripheral flange portion disposed between` said ceramic iiange andthe interior of said envelope. ,l Y

8. A switch comprising a metallic envelope, a.

ceramic ein one end of said envelope having ther-- mal Contact about its peripheral surface with? the interior of said envelope, an electrodejcarriedn by said ceramic and radially insulated jjhereby,

and resilientsealing means comprising a disclike member having a periphera iiange disposed l0 about Ythe radially insulated part V9i said ,electrode. g

9. In combination, a switch comprising a `metallic envelope, a disc-shaped electrode dis-I posed in insulated position in one end of said *V envelope and extending transversely across said envelope, a planar` insulating runwaybetween said electrode and the interior surface of said envelope, and a body of mercury movable along said runway upon tilting of the envelope toward said electrode and having a straight line advancing edge extending transversely across said runway normal toethedirection of movement of said mercury. i; 10. A switchcomprising a metal envelope hat;- ing a ceramicrinsert seated in one end thereof,

said insert carrying at its outer end are electrode radially insulated thereby from saldi-envelope, resilient sealing means closing the insert end of said envelope about-said electrode and radially overlapping said one end off said insert, and means for axially compressing said sealing means in position whereby said insert isV entirely under compressive stress. l 'e e 11s-The combination, in a metal Venvelc'gie switch havingf a square envelope section and an enlarged cylindrical end portion, of a ceramic disposed in said enlarged end; portion having an axially extending outwardly projecting iiange, an annular shoulder spaced radially inwardly of said ange, and a frusto-oyramidal recess extending from the inner. end of said ceramic toward said shoulder and@ having its small end terminating radially inwardly of said shoulder andrspaced axially inwardly thereof. i

i2'.Y A ceramic insert for a mercury switch of the class described comprising a thermal conductive refractory having an axially extending irusto-pyramidal recess in one end thereof 'terminating inwardly ci said end in a rectangular radial groove of a depth and width suchras to retain a stable body of mercury therein, said groove. having the side away'from "said recess defined by the planar face of an electrode supported entirely in the .opposite end of rsaid ceramic. Y fY i3. In combination, a metal envelcpe switch oi' the class described havingja ceramic insert in one end thereof, sealing means for the outer end ci said insert, `a compression ring engaged bythe spun' over end of said envelope for pressing said sealing means against said insert, a contact lug washer held in position by said ring and ingelectrical engagement with said envelope, anfrelectrode carried by said insert, a ccnductoroonnected to said washer, a conductorgconnected to said electrode, a spacing insulatorbetween said conductors and carried by sacid electrode, and a two piece mouldedhousing enclosing said switch and having an annular joint provided with openi trical engagement with ysaid envelopera'n electrode carried by said insert and having an axially projecting stud, a terminal lug on said stud, conductors connected to said washer and said lug, insulating spacing means on said stud separat- 5 ing the ends of said conductors, and atwo-piece moulded housing enclosing said switch and havof said envelope andY having keying engagement at its edge with said first part, and individual openings in each part adjacent the meeting edges 2o thereof whereby said conductors may be 'led out from said switch in any desired angular relation; Y e i j,

16. A contact lug retaining washeg adapted to be compressed between the spun-over edge of a 25 metal envelope and the ceramic insert in a mer- 'cury switch Yof the class described,-r comprising a washer-like ring having an integralY radial proi jection provided at its free end with lateral projecting ears, said ears being bent over to form a 3Q;

conductor socket and said projection beingbent over toy dispose' the axis of said socket in a plane sulstantially parallel to the plane oi said washer.

17. In combination, a metallic switch envelope having a body portion 'andan enlarged end por- 35' tion defining therebetweenan annular shoulder,

a ceramic insert in said end portion having its inner end seated against said shoulder to limit inward movementfof said insert, an axially vextending ange on Vthe outer end ofsaid insert g spaced radially inwardly of the interior surface ofE the end portion of said envelope, an axial bore in said insert terminating at its outer end in successive "annular shoulders, an electrode disc disposed :within said ange andseating against 45 i one of said shoulders to limit inward movement -thereof, and resiiient sealing .means havinga disc-'shaped portin engaging the nouter faces of said electrode andange and havinga peripheral flange extending into the annular space jbetween 50 said end portion of said envelope'and sai ange ci said insert. i

18. In combination, a metallic switch envelope having aiody portion and an en arged end portion dening therebetween an annular shoulder, 55 a ceramic insert in said end portion having its inner end seated against said shoulder to limitl inward movement of said insert, an axially. extending "iiange on the outer end of said inserti spaced radially inwardly lof the interior surfacei 30 of the end portion oi said envelope, an axial bore said insert terminating at its outer end in successive annular shoulders, an electrode disc disposed within said flange and seating against one of said shoulders to limit inward movement thereof, resilient sealing means having a disc-shaped portion engaging the outer faces of said electrode and ange and having a peripheral iiange extendingY into the annular space between said ene't portionof said envelope and said ange of said insert, and a relatively rigid insulating -disc compressed against the outer radial face of said sealing means to produce axiaigand radial compression oi said sealing means on said ange and electrode.

ananas 19. In combination, a metallic switch envelope having a body portion and an enlarged end por- `tion defining therebetween an annular shoulder,

a ceramic insert'in said end portion having its inner end seated against said shoulder to limitposed within said ilange and seating against one x of said shoulders to limit inward movement thereof, said disc having an axial thickness such that the outer radial face thereof is coplanar with the outer end of said ilange, and resilient sealing means having a disc-shaped portion engaging the outer faces of said electrode and ilange and having a peripheral flange extending into the annular space between said end portion of said envelope and said ange of said insert.

20, In combination, a metallic switch envelope having a lbody portion of square form and an enlarged cylindrical' end defining therebetween a shoulder, a ceramic insert having its inner end seated against said shoulder, a frusto-pyramidal` recess in said insert, means foraligning said insert with said envelope to maintain the defining surfaces of recess in register with the interior deilning surfaces of said body portion, an electrode supported in said insert at the end of said recess removed from said body portion, and a body of mercury in said body portion and movable along the lower deilning surface of said recess with an advancing edge extending normal to the direction of movement thereof toward and away-from said electrode.

21. In a `metallic envelope type of mercury switch, a ceramic insert havinga frusto-pyramidal 'recess terminating at its small end in a rectangular radially offset groove, an axially extending annular flange on said insert disposed radially and axially outwardly of said groovefa disc-shaped electrode seating in said flange and forming'one deilning wall of said groove.' a body of mercury in the lower side of said groove and projecting radially inwardly beyond the adjacent edgeof the lower defining surface of said recess, and an axial recess in the face of said electrode receiving a portion oi said mercury to increase the area of contact between said mercury and said electrode.

22. In combination, a metal envelope switch of the class described having a ceramic insert in one end thereof, sealing means for the outer end of said insert, a compression ring engaged by the spun over end of said envelope for pressing said sealing means against said insert, a contact lug washer heldin position by said ring and in electrical engagement with said envelope, an elec' trode carried by said insert, a conductor connected to said washer, a conductor connected to said electrode, and a spacing insulator between said conductors and carried by said electrode.

23. In combination, a metal envelope mercury switch having a ceramic insert in one end thereof, compression means for holding said insert in position including a terminal lug washer in electrical engagement with'said envelope, an electrode carried by said insert and having an axially projecting stud, a terminal lug on said stud, conductors connected to said washer and said lug,

and spacing means on said stud separating theends of said conductors.

24. In a metallic envelope type of mercury switch, a ceramic insert having a frusta-pyramidal bore extending axially therein and terminating at its smaller end in an acutely angled straight line transverse cutting edge extending the width of said smaller end, a radially outwardly extending wall defining said edge, an axial wall disposed at the outer end of said radial wall extending parallel to said edge, a second radially denne Ywithsaid last-named wall and said axiall wall a rectangular groove extending the full.

width of the smaller end of said recess.

PAUL S. BEAR. 

